The ability to measure the amount of liquid in a volume of gas is extremely important. Numerous occasions require the accurate measurement of the amount of liquid in a gas. Such accuracy is extremely important to buyers and sellers of natural gas. If the gas contains water, a buyer does not want to pay for the gas on the basis of the gross volume shipped to him. Rather, he wants to pay only for the net amount of gas present in the total volume delivered. On the other hand, if the gas contains "natural gas liquids" or condensates, the seller wants to be compensated for this energy-rich liquid. In both cases, it is very important to know the gas and liquid fractions. Net gas measurement is also required in production fields.
There are a number of instruments which have been used to make various types of measurements. Techniques are available to measure the properties of a mixture. For example, the conductivity of the mixture may be measured at a relevant frequency.
Radiation is grouped into three general categories: electromagnetic, mechanical, and particle radiation. Mechanical radiation requires a material medium to propagate energy from one place to another. For example, sound, produced by vibration, cannot travel through a vacuum, but does travel freely through gases, liquids, or solids. Since mechanical radiation is primarily produced by vibration, detectors of this kind of radiation are typically things that vibrate, such as the diaphragm in a microphone, telephone, or transducer. Mechanical radiation in the form of ultrasound is a valuable tool in measurement technology.
For the purpose of the present invention, generally, sounds above approximately 20,000 hertz are defined as ultrasound. Ultrasound has been used to identify flaws in industrial parts, to diagnose and treat diseases, and to explore the ocean's depths. Ultrasonic waves can be generated by mechanical, electromagnetic, and thermal devices with frequencies ranging from 20,000 to several billion hertz.
The field of ultrasonics involves producing vibrational waves of above 20,000 hertz in solids, liquids, gases, and other elastic materials. High-power applications include ultrasonic welding and drilling. Ultrasonic waves are frequently used to detect internal defects in solid materials. For example, railroads use ultrasonic waves to locate cracks within railroad tracks. With particular emphasis to the present invention, ultrasonics are used in flow metering technology.
It is appreciated that the present invention is applicable for solids, liquids, gases, and other elastic materials. As used for the present invention, the terms liquid and condensate are used interchangeably. It is appreciated by those skilled in the art that all condensates are liquids, but all liquids are not condensates. For example, in the natural gas industry, a condensate is a hydrocarbon. More particularly, a condensate could be considered a liquid hydrocarbon lighter than fuel oil. Alternately, water is a liquid but not a condensate.
It is a feature of the present invention to provide an apparatus and method for determining the percentage of a liquid or condensate in a volume of gas flowing through a conduit and the associated flow rates.
Yet another feature of the present invention is to provide an apparatus and method for determining the percentage of liquid or condensate in a volume of gas where the amount of condensate present is in the range from 0 to 100 percent.
Yet another feature of the present invention is to provide an apparatus and method for determining the flow rate of liquid or condensate in a volume of gas where the amount of condensate present is in the range from 0 to 100 percent.
Still a further feature of the present invention is to provide a method and apparatus for determining the liquid or condensate content in a volume of gas and its associated flow rate by measurement of the volume's ultrasonic properties.
It is a further feature of the present invention to provide an apparatus and method for determining the percentages of gas, liquid or condensate in an gas, liquid, condensate mixture by measuring its ultrasonic properties.
Briefly stated, the foregoing and numerous other features, objects and advantages of the present invention will become readily apparent upon reading the detailed description, claims and drawings set forth hereinafter. Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will become apparent from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized by means of the combinations and steps particularly pointed out in the appended claims.